Cartridge casing

ABSTRACT

A cartridge casing comprises a casing tube and a head cap. The casing tube bounds at least part of the head cap. The head cap is being fixed relative to the tube by a welding process.

The present disclosure relates to a cartridge casing.

In particular it relates to a cartridge casing for a projectile.

BACKGROUND

A conventional cartridge casing 10 is shown in FIG. 1. The cartridge assembly 10 comprises a casing 12 and a projectile 14. The casing 12 has a hollow section 16 which will contain propellant for displacement of the projectile 14. The casing 12 further comprises a head 18 at the end opposite to the projectile 14 which comprises a chamber 20 for a percussion cap, and a flash tube 22 for communication of an ignition charge from the percussion cap to the inside of the casing 12 and thus the propellant. The walls of the chamber 16 are formed integrally with the head 18. Such a cartridge casing may typically be formed of brass. This material choice has many advantages, for example, it is relatively easy to form into the desired shape. However, brass has demerit in that it is also relatively dense, and hence the casing 12 forms a relatively large percentage of the mass of the whole cartridge.

It is beneficial to reduce the mass of cartridges in order to reduce transport costs and mass burden on soldiers who carry them.

Hence a cartridge case and a method of manufacture of a cartridge case which is of relatively low weight is highly desirable.

SUMMARY

According to the present disclosure there is provided an apparatus and method as set forth in the appended claims. Other features of the invention will be apparent from the dependent claims, and the description which follows.

Accordingly there may be provided a cartridge casing comprising: a casing tube having a first end; wherein the tube bounds at least part of a head cap entered into its first end; the head cap being fixed relative to the tube by a welding process.

The casing tube may be substantially cylindrical and have an internal diameter at the first end which receives the head cap; and the head cap may have an external diameter at least part way along its outer periphery sized such that it fits within the first end of the casing tube.

The relative dimensions of the internal diameter at the first end of the casing tube and the external diameter of corresponding region of the head cap may be such that when the head cap is located in the casing tube they form an interference fit with one another.

The casing tube may further comprise a corrugation towards the first end of the casing tube which extends at least part way around the circumference of the casing tube.

The corrugation may be provided spaced apart from the first end of the casing tube such that the inner circumference of the first end is substantially constant in a region between the first end and the corrugation.

When assembled, the head cap may extend along the inside of the casing tube towards the corrugation.

The external diameter of the outer periphery of the head cap that is configured to fit within the first end of the casing tube may terminate in an outwardly protruding shoulder, and when the casing tube and head cap are assembled, the casing tube may extend towards the outwardly protruding shoulder.

There may also be provided a cartridge comprising a projectile mounted to a cartridge casing according the present disclosure.

There may also be provided a method of manufacturing a cartridge casing comprising the steps of: forming a casing tube by a first process; forming a head cap by a second process; and joining the casing tube and head cap by third process.

The first process may comprise the steps of: providing a material sheet; and deforming the material sheet into a substantially cylindrical tube.

The material sheet may be deformed such that the cylindrical tube is open at a first end and closed at a second end opposite to the first end; and removing the closed end of the cylinder such that the tube is open at both ends.

The third process may comprise the steps of: entering the head cap into the first end of the casing tube; and bonding the head cap and casing tube together using a welding process.

The casing tube and head cap may be welded to one another by applying a welding process to the external surface of the casing tube, radially outward of where the casing tube is in contact with the external diameter of the head cap.

The casing tube and head cap may be welded to one another around a internal circumference of the casing tube at an interface between the casing tube and head cap.

The casing tube and head cap may be welded to one another by applying a welding process to an interface between the casing tube and head cap on the external surface of the casing tube and head cap.

Hence there is provided a light weight cartridge casing configuration and method of manufacture for a light weight cartridge casing.

BRIEF DESCRIPTION OF THE DRAWINGS

Examples of the present disclosure will now be described with reference to the accompanying drawings, in which:

FIG. 1 shows a conventional cartridge casing, as described previously;

FIG. 2 shows an example of a cartridge casing according to the present disclosure;

FIG. 3 shows an alternative example of a cartridge casing according to the present disclosure;

FIG. 4 shows an example process for the manufacture of a cartridge casing according to the present disclosure; and

FIG. 5 shows an example forming process for a casing tube of the cartridge casing of the present disclosure.

DETAILED DESCRIPTION

FIG. 2 shows an example cartridge casing 30 according to the present disclosure. The cartridge casing 30 comprises a casing tube 32 having a first end 34 which is closed by a head cap 36. The casing tube 32 is substantially cylindrical and has an internal diameter at the first end 34 which receives the head cap 36. The casing tube 32 bounds at least part of the head cap 36 entered into its first end 34. The head cap 36 is configured to support and reinforce the base of the casing tube 32 to prevent it from swelling and rupturing during operation. As will be described in more detail later, the head cap 36 is welded to the casing tube 32, thereby fixing the head cap 36 and casing tube 32 relative to one another.

In the context of the present disclosure, “welding” is intended to cover joining processes that produce bonding of materials by heating, which may be done with or without pressure or filler material. For example, the term is intended to encompass brazing and soldering. It may also be taken to encompass a process in which the material of one or more articles being joined are brought into a molten state to facilitate bonding. It may include a process in which the base materials melt along with a filler material.

The casing tube 32 further comprises a second end 38, which is open and configured to receive a projectile (as shown in FIG. 1) opposite to the first end 34. The second end 38 has a diameter which may be substantially the same as, or less than, the diameter of the first end 34. In the example shown the diameter of the second end 38 is substantially less than the diameter of the first end 34.

The walls of the casing 32 define a substantially cylindrical thin walled chamber 40. The tube casing 32 has a substantially constant diameter along a first region of its length between the first end 34 and the second end 38. However, the cylindrical thin walled chamber 40 may have a taper (for example <1°) along at least part or all of its length. That is to say, although having a substantially constant diameter along its length, the diameter of the casing 32 may decrease slightly in a direction away from the first end 34, reducing in diameter from the first end 34 to the second end 38. The casing tube 32 also comprises a transition region 42 towards or at the second end 38 wherein the transition region 42 of the casing tube 32 reduces in diameter in a direction away from the first end 34 to the second end 38. Hence the diameter of the casing tube 32 will be different on either side of the transition region 42. The diameter of the casing tube 32 is substantially constant along its length to either side of the transition region 42.

The head cap 36 defines a passage 46 which extends all of the way through the head cap 36 which in use will be a flash tube (or “flash passage”). The flash tube/passage 46 extends into a chamber 47 which, in use, will house a percussion cap (sometimes referred to as a “primer”). Thus the head cap 36 has a percussion side 48 which, in use, faces away from the casing tube 32.

The head cap 36 further comprises a charge side 49 which, in use, defines part of the internal surface of the cartridge casing 30. Thus the flash passage 46 extends between the percussion side 48 and the charge side 49.

The head cap 36 has an external diameter at least part way along its outer periphery sized such that it fits within the first end 34 of the casing tube 32. The relative dimensions of the internal diameter at the first end 34 of the casing tube 32 and the external diameter of corresponding region of the head cap 36 may be such when the head cap 36 is located in the casing tube 32 they form an interference fit with one another.

The casing tube 32 and head cap 36 may comprise a welded join which bonds them together in a region where they form an interference fit with one another. For example, the join may be provided around the circumference of the casing tube 32 and head cap 36 in a region where they interface with one another. Such a region is indicated with arrows “A” in FIG. 2. The join may be a through weld or stake weld.

Alternatively the casing tube 32 and head cap 36 may comprise a join which bonds them together in the interior of the casing tube 32, for example in a region around a circumferential edge of an interface between the casing tube 32 and the head cap 36. Such a region is indicated with arrows “B” in FIG. 2.

The weld may achieved by laser welding. Alternative weld joins may be provided which brought only material of the casing tube 32 into a molten state, or brought material of both the casing tube 32 and head cap 36 into a molten state. The weld join may have been provided by any one of the welding processes as hereinbefore defined.

An alternative example of a cartridge casing 80 according to the present disclosure is shown in FIG. 3. The example of FIG. 3 is similar in many ways to the cartridge case shown in, and as described with reference to, FIG. 2. Features common to the examples of FIG. 2 and FIG. 3 are referred to using the same reference numerals.

In the example of FIG. 3, the casing tube 32 further comprises a corrugation 50 towards the first end 34 of the casing tube 32. The corrugation 50 extends at least part of the way around the circumference of the casing tube 32. In the example shown, the corrugation 50 extends all of the way around the circumference of the casing tube 32. The corrugation 50 extends inwardly from the external surface of the casing tube 32, such that it extends into the chamber defined by the thin walls of the casing tube 32. The corrugation 50 provides an expansion feature for the casing 32 during operation of the cartridge casing 30′. The corrugation 50 may also be provided in the example of FIG. 2. The corrugation 50 may be provided as a convolution or cannelure which extends around the circumference of the casing tube 32. The corrugation 50 is provided spaced apart from the first end 34 of the casing tube 32 such that the inner circumference of the first end 34 is substantially constant in a region between the first end 34 and the corrugation 50. When assembled, the head cap 36 extends along the inside of the casing tube 32 towards the corrugation 50. In the example shown in FIG. 3, the external diameter of the outer periphery of the head cap 36 that is configured to fit within the first end 34 of the casing tube 32 terminates in an outwardly protruding shoulder 52. When assembled, the casing tube 32 extends towards the outwardly protruding shoulder 52 such that the first end 34 of the casing tube 32 is proximate to or abuts with the shoulder 52.

The casing tube 32 may be joined to the head cap 36 in the region of the protruding shoulder 52 (as indicated by arrow “C” in FIG. 3), the join being provided by a laser or other welding process as hereinbefore defined.

The convolution or cannelure 50 is provided to act as an expansion joint positioned just forward of the weld to eliminate stress on the weld join.

The casing tube 32 and head cap 36 may be formed from a metal, metallic material or metal alloy comprising, for example, aluminium or titanium. In one example the casing tube 32 and head cap 36 may comprise ferritic alloys, for example stainless steel. The casing tube 32 and head cap 36 may alternatively be formed from non metallic material and/or metal-plastic composite material. The casing tube 32 and head cap 36 may be made of the same or dissimilar materials. The choice of welding process will be determined in part by the choice of materials used, as appropriate and as understood in the art.

The method of manufacture of a cartridge casing 30, 30′ according to the present disclosure and as shown in FIG. 2 and FIG. 3 comprise the steps of forming a casing tube 32 by a first process, forming a head cap 36 by a second process and joining the casing tube 32 and head cap 36 by a third process. This is described as a flow diagram in FIG. 4. FIG. 5 shows the forming of the casing tube 32 in more detail.

A material sheet 100 for example a stainless steel strip 100, is formed on a transfer press into a tapered casing tube 32 as shown in FIG. 5. In an independent process a stainless steel wire, or blank of material, is machined and/or formed into a cylindrical head cap 36, perhaps by a cold forming process. The casing tube 32 and head cap 36 are joined in a third independent process, after the casing tube 32 and head cap 36 are assembled.

The material sheet 100 which may be deformed in a series of steps, shown in sequence from the bottom to the top of the page on FIG. 5 in the direction shown by the arrow 102. Although details of the process may vary, the material is gradually formed through intermediate stages in which the features of the casing tube 32 are provided. The thin walls of the cylindrical tube 32 are drawn from the material strip 100, during which process the tapered transitional region 42 may be formed. The material sheet 100 is deformed such that the cylindrical tube 32 is initially formed open at the first end 34 and closed at the second end 38 opposite to the first end 34.

Alternatively the casing tube 32 may be formed from a pre-drawn tube.

The transition region 42 of the cylindrical tube 32 is tapered towards the second end 38 such that the second end has a diameter less than that of the first end 34.

The second end 38 of the casing tube 32 is then removed such that the second end 38 is “open”.

The second process, for forming the head cap 36, comprises the step of providing the blank of material, machining and/or forming the material blank into the cylindrical head cap 36 such that the head cap 36 has an external diameter substantially identical to the internal diameter of the first end 34 of the casing tube 32 to thereby provide an interference fit between the two. Alternatively it may be formed with an external diameter slightly less than the internal diameter of the casing tube 32 such that the interference fit is negligible or completely absent. The head cap 36 is also formed with the passage 46 which extends all the way through the head cap 36.

The head cap 36 may be turned, or cold formed, or any other appropriate method for the forming of a head cap 36.

The third process may comprise the steps of entering the head cap 36 into the first end 34 of the casing tube 32. The casing tube and head cap 36 are then bonded together using a welding process.

The casing tube 32 and head cap 36 may be welded to one another in a region where they form an interference fit with one another. For example, they may be welded to one another by applying a welding process around the circumference of the casing tube 32, on the external surface of the casing tube 32, radially outward of where the casing tube 32 is in contact with the external diameter of the head cap 36. Such a region is indicated with arrows “A” in FIG. 2. This may be achieved by a through weld or stake weld process.

Alternatively the casing tube 32 and head cap 36 may be welded to one another around the internal circumference of the casing tube 32 at an interface between the casing tube 32 and head cap 36, as indicated by arrows “B” in FIG. 2.

With reference to the example of FIG. 3, the casing tube 32 may be welded to the head cap 36 in the region of the protruding shoulder 52 (as indicated by arrow “C”) by a butt weld or other welding style. That is to say the casing tube 32 and head cap 36 are welded to one another by applying a welding process to an interface between the casing tube 32 and head cap 36 on the external surface of the casing tube 32 and head cap 36.

In each example, the welding process may be any one of the welding processes as hereinbefore defined. For example the welding process may be one of laser welding. Alternative welding processes may employed which bring only material of the casing tube 32 into a molten state, or bring material of both the casing tube 32 and head cap 36 into a molten state.

Prior to assembly the casing tube 32 and head cap 36 may be prepared for welding, for example being degreased. Post welding, no subsequent machining may be required, and neither may a cleaning of the casing be required.

Post welding the cartridge 30, 30′ may be turned to ensure the head cap 36 is properly centred on the casing tube 32, and to provide any other additional features required for successful functioning of the casing 30, 30′. The assembly is then gauged to ensure it meets the correct dimensional tolerances.

Thus there is provided a thin cartridge casing with a thin wall casing tube which is made of a material which is inherently lighter than conventional cartridge cases. The material choice enables the casing tube to withstand the ignition pressures induced during operation whilst also being made by a reliable and repeatable manufacturing process. Since the casing may have a thinner wall than that of the related art, and is made of a material which has a lower density than that used for conventional casings, the resultant cartridge casing will overall be lighter than an equivalent conventional casing. Hence for a given amount of powder propellant, a cartridge having a casing of the present disclosure will produce the same performance for less overall cartridge mass than a conventional cartridge assembly. Additionally, a cartridge casing of the present disclosure may contain a larger volume of powder propellant for delivering the projectile over a further distance or with greater force than a conventional cartridge, and yet, when assembled, be of the same mass or lower than a conventional cartridge.

While the cartridge cases have been described with reference to propelling a projectile, the techniques and materials described may also be used in the production of a blank cartridge case, for example one used to contain only a charge but no projectile.

Attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed. 

1. A cartridge casing comprising: a casing tube having a first end; wherein the casing tube bounds at least part of a head cap entered into the first end; and wherein the head cap is fixed relative to the casing tube by a bond provided by a laser welding process around an internal circumference of the casing tube at an interface between the casing tube and head cap.
 2. A-The cartridge casing of claim 1 wherein: the casing tube is substantially cylindrical and has an internal diameter at the first end which receives the head cap; and the head cap has an external diameter at least part way along its outer periphery sized such that it fits within the first end of the casing tube.
 3. The cartridge casing as of claim 2 wherein the relative dimensions of the internal diameter at the first end of the casing tube and the external diameter of corresponding region of the head cap are such when the head cap is located in the casing tube they form an interference fit with one another.
 4. The cartridge casing of claim 1 wherein the casing tube further comprises a corrugation towards the first end of the casing tube which extends at least part way around the internal circumference of the casing tube.
 5. The cartridge casing of claim 4 wherein the corrugation is provided spaced apart from the first end of the casing tube such that the internal circumference of the first end is substantially constant in a region between the first end and the corrugation.
 6. The cartridge casing of claim 5 wherein, when assembled, the head cap extends along the inside of the casing tube towards the corrugation.
 7. The cartridge casing of claim 6 wherein the external diameter of an outer periphery of the head cap that is configured to fit within the first end of the casing tube terminates in an outwardly protruding shoulder, and when the casing tube and head cap are assembled, the casing tube extends towards the outwardly protruding shoulder.
 8. A cartridge comprising a projectile mounted to the cartridge casing of claim
 1. 9. A method of manufacturing a cartridge casing, comprising the steps of: forming a casing tube by a first process, the casing tube having a first end; forming a head cap by a second process; and joining the casing tube and head cap by a third process including entering the head cap into the first end of the casing tube wherein the casing tube bounds at least part of the head cap entered into the first end, and bonding the head cap and casing tube together using a laser welding process around an internal circumference of the casing tube at an interface between the casing tube and head cap, such that the head cap is fixed relative to the casing tube by a bond provided by the laser welding process.
 10. The method of claim 9 wherein the first process comprises: providing a material sheet; and deforming the material sheet into a substantially cylindrical tube.
 11. The method of claim 10 wherein: the material sheet is deformed such that the cylindrical tube is open at a first end and closed at a second end opposite to the first end; and removing the closed end of the cylindrical tube such that the cylindrical tube is open at both ends.
 12. The method of claim 11 wherein the casing tube and head cap are welded to one another by applying a welding process to the external surface of the casing tube, radially outward of where the casing tube is in contact with the external diameter of the head cap.
 13. The method of claim 9 wherein the casing tube and head cap are welded to one another by applying a welding process to an interface between the casing tube and head cap on the external surface of the casing tube and head cap. 